The invention relates to compositions which crosslink to give elastomers, to a process for their preparation and to shaped articles produced from these compositions.
Compositions which crosslink to give elastomers and which are said to have a low compression set are already known. EP 432 761 describes peroxide-crosslinking silicone elastomers to which an alkenylsilazane is added. EP-A 415 180 describes peroxide-crosslinking organopolysiloxanes with cerium compounds or magnesium oxide. U.S. Pat. No. 4,774,281 describes peroxide-crosslinking organopolysiloxanes which are crosslinked using hot air vulcanization. EP-B 0 377 185 describes a composition which is composed of a number of parts, where one part is a diorganopolysiloxane containing vinyl groups, another part is an organohydrosiloxane and an additional part is a platinum catalyst, and an organic peroxide which is present in amounts of at least 0.2% by weight. According to EP-B 0 377 185, the pot life of the catalyzed mixture is improved by cyclic vinylmethylsiloxanes.
All of these compositions have the disadvantage that either the compression set is too high or the reproducibility of the compression set after storage is too low.